gh-101819: Fix _io clinic input for unused base class method stubs (#104418)

gh-101819: Fix _io clinic input for unused base class method stubs (#104418)

When preparing the _io extension module for isolation, many methods were
adapted to Argument Clinic. Some of these used the '*args: object'
signature, which is incorrect. These are now corrected to an exact
signature, and marked unused, since they are stub methods.